This proposal explores the neural and psychological mechanisms of cognitive control. Control processes are thought to be the fundamentally important in enabling the flexibility, complexity, and sophistication of human cognition. Conversely, breakdowns in cognitive control are a major source of impairment in a wide range of neuropsychiatric disorders, such as Alzheimer's and Parkinson's Disease, schizophrenia, and ADHD. A core component of cognitive control is the ability to be proactive - to prepare attention, thoughts, and action in advance based on foreknowledge, expectations, or goals regarding upcoming events. A large body of work has elucidated the neural systems involved in proactive or preparatory control, with current consensus pointing to the importance of dorsal frontoparietal circuits, along with the midbrain dopamine system and medial frontal cortex. Nevertheless, theoretical progress in specifying of the precise functional contributions and interactions of these systems has been slow. Our previous work has demonstrated that challenges for theoretical understanding arise because there are multiple possible control mechanisms that can be flexibly deployed according to the specific task demands, and other factors such as stable individual differences, motivational factors, and the integrity of specific neural control systems. The current proposal tests the hypothesis that important qualitative distinctions exist between preparation based on: a) attentional vs. intentional control; b) intentional vs. volitional control; and c) representations at different levels of a goal hierarchy. These hypotheses will be tested in an integrated series of behavioral and neuroimaging studies (using state-of-the-art functional magnetic resonance imaging methods and analytical techniques) that systematically examine these distinctions from within a common set of experimental paradigms, in both young and older adults, and in relation to individual difference variables. Success in this work would represent a significant theoretical advance, by clarifying the neural mechanisms and behavioral consequences of how control over cognition is achieved. This project has high relevance for public health in terms of the potential to provide critical information regarding the neural and psychological bases of both the transient lapses and sustained impairments in cognitive control suffered by both healthy individuals and clinical populations. Such knowledge could be used to drive the development of more effective interventions